This invention relates generally as indicated to improved concrete structures for use in shore protection and/or wave control and the method of making same. More particularly, such invention is concerned with the making of concrete structures which may be similar in shape to previous known concrete structures but which have improved strength characteristics and can be mass produced more easily and economically than heretofore.
The shorelines along lakes and rivers as well as along coastal regions are being eroded away at an alarming rate. Numerous methods have been tried in an attempt to control this problem with mixed results. An acceptable method of shore protection for flat or moderate offshore slopes is to construct a breakwall or offshore breakwaters some distance from the shoreline. Such a breakwall can be constructed of any material capable of withstanding the wave energies impinging on them, including stone, gabions, steel, wood, and concrete shapes.
One objection to most concrete structures is their relatively high cost of manufacture and transporting to the site where they are to be installed. One such concrete structure is generally in the shape of a block which is typically precast at a manufacturing location and then transported to the job site, which greatly adds to the cost of the installation.
Another concrete structure that has been effectively used in certain installations is called a dolos or dolosse (plural). Such dolosse are also typically precast at a remote location and transported to the site for installation at substantial expense. The conventional dolos consists of two cross members which extend generally perpendicular to each other in different planes and are connected together by an intermediate member at their midpoints. Each cross member is tapered in opposite directions from the center to the ends thereof, and is generally octagonal in cross section, having eight flat sides extending around the periphery and relatively sharp angled edges where the octagon sides meet. Any number of these dolosse can be randomly piled one on top of the other with the cross members overlapping each other to form a relatively stable structure which is effective in absorbing and dispersing wave energies.
Another possible objection to the use of such conventional dolos is the relatively sharp angled or fluted edges where the octagon sides meet which set up stresses where weakness and fracture could result.
Also, metal forms were typically used to make such concrete structures, which not only requires a relatively high capital investment but such metal forms have a relatively short useful life. In addition, such metal forms require high maintenance and repair, and are difficult to clean.
A further objection to the use of metal forms is that they cause air and moisture to be entrapped at the surface of the concrete structures resulting in reduced surface strength.